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2000Mghz RAM, XMP profile and super-high QPI voltage

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October 16, 2010 5:00:57 AM

Ok so I just finished building my new rig - Asus Rampage III Formula, Core i7 950 and 6GB, 2000Mghz Kingston HyperX. At first I want to try if everything works at it's rated speed, so I simply went into the BIOS and chose XMP Profile 1 - the speed, timing, and voltage for the ram at the advertised specs.
Everything works indeed, except the fact that the QPI/Dram core voltage was set at 1.7V! I noticed it because the BIOS was showing it in red... I've read that when OCing, QPI voltage should be maybe around 1.3V, but when I tried setting it manually the PC refused to even boot into windows with anything less than 1.5V! Why is the XMP preset at such a high voltage?! Isn't that going to damage something?
What can I do now - I got this nice and fast ram and I'm afraid to run it at that voltage :??: 
I really need some advice on this one.... It's still not too late to return the ram if it comes to it...
a b } Memory
a c 100 K Overclocking
October 16, 2010 5:27:26 AM

XMP just sets what it needs.... in this case, to run 2000mhz it needs 1.7V. It definitely needs a base clock of 200mhz... and the default is 133mhz (at least on my i5 but I think they run the same base clock with different multipliers). Basically that's a very large OC. You should either turn off turbo boost and go with 4ghz flat or else even downclock to 3.6 or 3.8ghz. Alternatively, slow down the RAM.

Just a guess that the RAM is 2000mhz CL9. So you could easily run it at 1800mhz CL8, 1600mhz CL7, or 1400mhz CL6 depending on what baseclock you use. All these will have very close performance, because while you are losing RAM speed you gain latency (ie: faster response time).

So, don't use XMP. OC your CPU where you want it, then from there figure out the best RAM speed and timings you can get.

As an example, my RAM is 1600mhz CL8. I run it at 1416mhz CL7 and it's super fast as is. The reason for this is that I'm running 177 base clock which I found to be pretty much the highest I can go with turbo enabled (and keeping voltages normal... instead of 1.7 lol). RAM multipliers are 10, 8, and 6. At 10x, it would be 1770mhz CL9 but I could go 1800mhz CL9 or maybe a little more, so it would be a waste of at least 30-40mhz at that latency. At 8x, 1416mhz CL7, it's actually maxing out the speed I can reach at CL7. I did use 178x8 for 1424mhz CL7 but needed a tad more than 1.65V to be stable.

So, yeah, you RAM is fine and probably can be super fast (at least 1 latency faster than mine) you just need to manually sort it out. That's all part of overclocking. Not sure if you knew this, but literally any RAM speed above 1333mhz is overclocked, by specification. Basically having such fast RAM as yours just gives you more options for overclocks and a lot of speed.
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October 16, 2010 6:13:09 AM

Well, the Bclk at this huge ram OC is only 143Mhz... I'm not sure how this works - this is my first experience with the core i7. This BIOS Asus uses looks very strange to me - I can't find the memory multiplier, and I can't find the option to turn Turbo off :( 

Anyway, with the XMP set, the ram is running at 2006Mhz (timings 9-10-9-27), the CPU at 3146Mhz and the Bclk at 143. The CPU ratio is 22. Everything else is at AUTO. So I guess this XMP is trash and I should try and get my hands dirty and do some OCing the hard way :) 

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a b K Overclocking
October 16, 2010 6:25:13 AM

3BRP said:
Well, the Bclk at this huge ram OC is only 143Mhz... I'm not sure how this works - this is my first experience with the core i7. This BIOS Asus uses looks very strange to me - I can't find the memory multiplier, and I can't find the option to turn Turbo off :( 

Anyway, with the XMP set, the ram is running at 2006Mhz (timings 9-10-9-27), the CPU at 3146Mhz and the Bclk at 143. The CPU ratio is 22. Everything else is at AUTO. So I guess this XMP is trash and I should try and get my hands dirty and do some OCing the hard way :) 


Your last statement is absolutely correct, often these profiles (XMP) are designed just to make it work, even if that overvolting stuff, Its best to set them manually, lower voltages= longer life time, and you can fine tune latency and speed settings to get the best performance.
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a b K Overclocking
October 16, 2010 2:16:51 PM

..... My Muskin 2000mhz kit's XMP profile had the QPI voltage at 1.175.......
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November 20, 2010 4:33:08 PM

Rofl_My_Waffle, what you are talking about? I have just checked over thirty SPD dumps with XMP 1.2 from various memory vendors and all of them with QPI=1.60V.
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